Automated windowing and application of image processing techniques to input images, particularly scanned images, is to a certain extent known. However, it is also known that the automated application of image processing and enhancement to documents often results in undesireable image artifacts. In many cases, these artifacts are detectable by a viewer of the resulting or printed image.
As indicated by U.S. Pat. No. 6,240,245 to Fan et al., issued May 29, 2001, hereby incorporated by reference in its entirety, it is known in the art to take a page of image data and to separate the image data into windows of similar image types. For instance, a page of image data may include a halftone picture(s) with accompanying text describing or related to the picture. In order to efficiently process the image data, it is known to separate the page of image data into at least two windows, a first window representing the halftone image, and a second window representing the text. It is also possible, as will be described herein, to treat text as part of the image or document “background” and to characterize halftones, graphics, line art, etc. as bounded by a window or window boundary.
Processing of the page of image data can then be efficiently carried out by tailoring the processing to the type of image data being processed. In other words, in automatically processing of the page, it is likely to be desireable to process the windowed halftone and other non-background portions of an image in a manner different from the background. In such systems, the image processing techniques are frequently applied, or at least suggested, automatically to enhance the image for its ultimate rendering or display. The various image processing operations that can be carried out include, but are not limited to filtering, compression, color and tonal reproduction curve (TRC) correction, enhancement (edge) and adjustment, and halftoning. As will be appreciated, such processing may also be carried on with specific windows or regions, or the parameters of such processing may be altered from one window to another.
One aspect of the disclosed system and method deals with a basic problem in automated image processing—that of improperly segmenting or windowing the image and as a result producing artifacts or other undesireable changes in portions of the image. This aspect is further based on the discovery of a technique that alleviates this problem. The technique is applied to a segmented or windowed image, and seeks to determine whether the window boundaries are leaky. As used herein the term “leaky” is intended to characterize the nature or quality of an identified window or window boundary within a segmented image. Leaky implies that the boundary is, at least to a certain extent, indefinable or indeterminate. In such situations, as will be described with examples set forth below, the desired location of a boundary that separates the background from an enclosed graphic, halftone, etc. is not completely determinable. One example of where such a situation might occur is where a “bleeding” transition has been employed (i.e., where the graphic or image fades into the background), such as depicted in the exemplary image of FIG. 4. The disclosed system and method address such problems by seeking to determine if window boundaries are leaky, and if so, to compensate for the leaky boundaries in any image enhancement or processing that is done.
Disclosed in embodiments herein is a window segmentation method for classifying data defining an image into background and at least one non-background region, comprising: evaluating the data defining the image and segmenting the image into at least one background region and a non-background region, wherein said non-background region is bounded by a window having a boundary; and determining whether said window boundary is a leaky boundary
Disclosed in further embodiments herein is a window segmentation method for classifying data defining an image into background and at least one non-background region, comprising: evaluating the data defining the image and segmenting the image into at least one background region and a non-background region, wherein said non-background region is bounded by a window having a boundary; and determining whether said window boundary is a leaky boundary, wherein determining whether said window boundary is a leaky boundary comprises, performing edge detection along the window boundary to determine the presence or absence of an edge, comparing the length of any portion of the window boundary in which an edge is not detected, and in the event that the length of any missing edge portion exceeds a threshold, characterizing the window boundary as a leaky boundary.
Also disclosed in embodiments herein is an image processing system, comprising: memory for storing digital image data; a processor, connected to said memory, for evaluating the digital image data and segmenting the image into at least one background region and a non-background region, wherein said non-background region is bounded by a window having a boundary, determining whether said window boundary is a leaky boundary, and enhancing the image data as a function of the type of window boundary determined to be present in the image; and an output engine for rendering an enhanced image.
The system and methods will be described in connection with a preferred embodiment(s), however, it will be understood that there is no intent to limit the scope of the appended claims to the embodiment described. On the contrary, the intent is to cover all alternatives, modifications, and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims.